It is now established that islet replacement therapy is a viable approach for treatment of patients with various disorders. These include cancer patients undergoing upper abdominal exenteration (Tzakis, et al., Lancet 336: 402-405 (1990)); pancreatitis (Clayton, et al., Transplantation 76: 92-98 (2003); Farney, et al., Surgery 110: 427-437 (1991); Fontes, et al., Transplant Proc 24: 2809 (1992); Obenholzer, et al., Transplantation 69: 1115-1123 (2000); Robertson, et al., Diabetes 50: 47-50 (2001)), and insulin-dependent patients, where islet transplantation is a therapeutic option (Goss, et al., Transplantation 74: 1761-1766 (2002); Ricordi, et al., Transplantation 75: 1524-1527 (2003); Ryan, et al., Diabetes 50: 710-719 (2001); Shapiro, et al., N. Engl. J. Med 343: 230-238 (2000)).
Due to the usefulness of islets in therapy, as is indicated, supra, there is, of course interest in developing ways to isolate them. While there are many reports on isolation of islets using the automated method (Brandhorst, et al., Exp. Clin. Endocrinol Diabetes 103 Suppl. 2: 3-14 (1995); Cui, et al., Cell Transplant 6: 48-54 (2001); Marchetti, et al., Transplantation 52: 209-213 (1991); Miyamoto, et al., Cell Transplant 7: 397-402 (1998); Nielsen, et al., Comp. Med. 52: 127-135 (2002); Swanson, et al., Hum. Immunnol 62: 73 9-749 (2001); Toomey, et al., Brit. J. Surg. 80: 240-243 (1993); Toso, et al., Cell Transplant 9: 297-305 (2000); Wennberg, et al., Transplant. Proc. 33: 2537 (2001)), isolation of islets remains notoriously difficult. For example, Bosta, et al., J. Investig Med 43: 555-566 (1995); Krickhahn, et al., Cell Transplant 11: 827-838 (2002); Krickhahn, et al., Ann Transplant 6: 48-54 (2001), O'Neil, et al., Cell Transplant 10: 235-246 (2001), and White, et al., Horm. Metab. Res 31: 579-524 (1999), all discuss problems with respect to this.
The manufacture of macrobeads which contain secretory cells and/or organelles, such as cancer cells, islets, and so forth, is well known. See, e.g., U.S. Pat. Nos. 6,818,230; 6,808,705; RE 38,027; 6,303,151; 6,224,912; 5,888,497, and 5,643,569, as well as published U.S. Patent application 2005/0096561, all of which are incorporated by reference.
Agarose is used to encapsulate the biological materials in these patent documents after which the resulting structures are further encapsulated with a second layer of agarose.
Those familiar with agarose recognize that there are many types and varieties of this material available. One such type of agarose, is described in U.S. Pat. No. 4,983,268, the disclosure of which is incorporated by reference. It has a sulfate content of less than 0.2 wt % but greater than zero, a pyruvate content of 0-0.1 wt %, and a Kjeldahl nitrogen content of 0-0.04 wt %. The gels formed from the agarose exhibit a gel strength of at least 1200 g/cm2 (1.0 wt % concentration), substantial absence of DNA binding in 0.07 M or less tris acetate buffer, and an electroendosmosis (EEO) at 1.0 wt % agarose concentration of 0.05 or less.
There is an ongoing need to have improved versions of the materials first described in the patents and application set forth supra. It has now been found that use of agarose with the composition described supra results in a product that is unexpectedly superior to prior art products.
Details of the invention are set forth in the disclosure which follows: